Corrosion resistant alloy



Patented Aug. 20, 1940 PATENT OFFICE 2,212,266 coaaosIoN RESISTANT ALLOY Henry L. Coles, Boulder, 0010,, assignor to William Sokolec, Chicago, Ill.

' No iii-swing. Application July 14, 1938,

. Serial No. 219,155

3 Claims: (01. 75-138) This invention pertains to a novel alloy that has many new and improved characteristics that' make the alloy particularly advantageous for various uses or purposes, and especially when 6 used in the cooking utensil field. The invention also pertains to an improved cooking utensil with new and improved characteristics.

More particularly the invention relates to nonferrous alloys having aluminum as a major elel ment.

It has been found in researches and experiments, and uses based on theresults thereof, that certain improvements and characteristics of a novel nature in these alloys and products have 15 been developed. Among the improvements is a very noticeable advance in resistance to corrosion, and especially is this clearly noticeable in cooking utensils made from this novel alloy.

, this alloy has shown greater resistance to than 0th r alloys heretofore known. Im-

to a r degree. It is recognized that there are many different alloys that have been presented as being corro- 25 sion resistant and it is known that some of them contain aluminum. However, the results herein of the research, experiments, and the confirming uses thereof, show that this new alloy sharply indicates a very marked increase in its resistance to corrosion over other alloys.

Certain additional characteristics of this alloy have developed, especially as to the workability of the sheets, bars and rods formed of the 85 alloy. It has been found that deterioration does not take place when fabricating this alloy into desired products. The toughness of the resulting alloy has been greatly increased, and a new ratio of quantities of the elements or constitu-. ents in the alloy has been developed to determine the best percentages of the constituents to obtain substantially maximum toughness.

' Further, the results of the researches, experiments and confirming uses have developed the ,most satisfactory and efllcient amounts'oi the several constituents of the improved alloyso as to give the improvedcorrosion resistance, obtain great toughness, and have eificient workability without deterioration.

The features of this invention are, therefore, to provide a novel alloy that has the characteristics and advantages above pointed out as to corrosion resistance, toughness and workability,

while at the same time to eliminate the disadvantages of colorization and easy denting and ,many and various uses.

the like when cooking utensils have been made and used of this improved alloy.

This invention, therefore, pertains to a novel alloy, and to an example of use thereof in which this alloy has shown great advantage. This ex- 5 ample is that of cooking utensils.

It is to be understood, however, that there are many other uses of the alloy and products made therefrom. Such, for instance, as the sheet, bar and rod pieces of soda fountains, and for particular products such as sterilizing cabinets, carts, instruments and accessories for operating rooms, in the hospital field, and for sheet or plates or bar elements in food handling and storage, and cooking apparatus. Also, there is a very large, use for this improved alloy in apparatus have been selected for the purpose of this description, i. e., cooking utensils, it hasbeen noted that a feature of the invention is to produce novel cooking utensils and other novel products which have high capacity for performing their work or functions without breaking or deteriorating, and at the same time are very tough and are highly non-corrosive.

In cooking utensils that have been heretofore produced, it has been found that some of them will not last very long, that they corrode easily and are consequently diflicult to keep sanitary and clean, that some of themido not have the strength to retain their original shape or de- 85 sign. It is found that in this latter group some of the utensils are easily dented and broken. Many other disadvantages have made themselves apparent when the utensil is employed in For instance, when a utensil is made sufiiciently strong to withstand the largestnumber of uses it is found that it is too heavy and ungainly in structure and cannot meet the price competition of other products which are designed for more specific and a 5 smaller number of uses. It, on the other hand, the utensil is made to meet the price competition it-does not have the strength and toughness to satisfy the number of desired uses for the product.

It is. therefore, another feature of this invention to provide an improved cooking utensil and other products that have the ability to be employed in a great number of uses, and to withstand the ordinary and extraordinary'uses that they may be-subjected to and not corrode or lose their shape or be broken. It has been found that the improved utensil products herein set forth are greatly improved in strength. and toughness and are resistant to corrosion and by reason of the composition of the alloy they may be fabricated at a much reduced cost and without loss or breakage. In accomplishing these desirable and satisfactory ends it is found that the improvements have a bearing on the elements or constituents of the alloy.

In producing the desired alloy it has been found that. the final alloy should have therein less than 1 per cent chromium. It also has been found, in producing the improved alloy and utensil and products, that the chromium may range between .60 to .90 'per cent. As a smaller range of the chromium it has been found that it may vary from .70 to .80 per cent, and in many uses it is desired that the chromium in the final product be approximately .75 per cent. It also has been found that when the chromium is approximately .75 per cent, that maximum toughness of the alloy is obtained.

In the molten alloy there will be a certain amount of impurities but these are considered as being negligible as they are usually found in trace form, or in smaller amounts.

Thus, the desired improved, high corrosive-resistant alloy with great toughness and ability to be fabricated shows, on analysis, that there is approximately less than 1 per cent chromium and the remainder aluminum.

In the production of this improved alloy and the preferred example, i. e., a cooking utensil, it is desirable to melt aluminum which, preferably, is of a purity better than 99.4 per cent, and

to add thereto chromic oxide so as to allow alloying between the two elements or constituents. Then the melt is poured and rolled into sheet, plate or bar form as desired, and to thereafter form the particularly desired shape or design of the desired cooking utensil.

More in detail and, as an example, the process or method of producing the improved alloy andutensil consists in melting, approximately, 100 pounds of aluminum which, preferably, has a purity of approximately 99.4 per cent. Thereafter chromic oxide, preferably in its powdered form .is added to; the surface of the molten aluminum and have the aluminum and chromium alloy together. In some instances it is desirable-to stir the melt intermittently so as to be quite positive to obtain a substantially uniform alloy and to thereby allow the reaction to take place automatically between the aluminum and chromium. The chromium oxide is" added in a quantity of 1 pounds or less to every ,100 pound of aluminum. By adding chromium oxide to the surface of the molten aluminum, it will be noted that the chromic oxide is heated indirectly for direct heat is applied to the container holding the aluminum and the chromic oxide will be heated by the aluminum rather than directly through the container.

After the alloying of the constituents the pouring of the molten metal takes place. Preferably, it is desirable to skim off the slag, or at least a majority of it before pouring. It is desired, in most instances, that there shall be substantially no slag in the' metal that poured.

After the pouring and cooling the alloy is rolled into desired sheets, plates or barsfrom which the desired cooking utensil is fabricated by being pressed, bent or drawn, or otherwise treated or worked to the final form or design.

It will be noted that the alloy and product are readily produced without an excessive number of steps in the process, and that there is a relatively small amount of chromium found in the analysis of the final alloy.

It will further be noted that by reason of experlments and uses, maximum toughness of this alloy is usually found when the chromium amount in the final alloy approximates .75 per cent. It will be noticed that there is a large quantity of low-melting point metal, and a small quantity of high-melting point metal employed. The final alloy has been found to be particularly adapted to being worked or fabricated without breaking and that it does not show deterioration by reason of such fabrication.

Cooking utensils made from the alloy have proven exceptionally valuable, and it is because they have shown a very marked increase in corrosion resistance and their increase in toughness that they are exceptionally and particularly desired in the industry. It is true that toughness is desired in all cooking utensils, and also the characteristic of an especially high resistance to corrosion. The alloy herein has met those requirements.

It will be understood that the improved-alloy gives great value and serviceability when made into products other than the product example herein. improved by employing the improved alloy herein.

and the preferred example, i. e., cooking utensils, and the method of producing both the alloy and the utensils have been set forth specifically, it is to be understood that variations and modifications may be made therein, and such changes and modifications are to be considered as being within the scope of this invention as set forth in the following claims.

I claim:

1. An aluminum-chromium alloy comprising .60 to .90' per cent chromium, and the remainder aluminum, the impurities being substantially negligible.

2. An aluminum-chromium alloy comprising, from .70 to .80 per cent chromium, and the remainder aluminum except traces of impurities.

3. A metallic alloy comprising, approximately, .75 per cent chromium, and the remainder aluminum except for traces of impurities.

' HENRY L. COLES.

Therefore other products are greatly- 

